Superbug MRSA uses 'double defence' to protect itself against antibiotics

Discovery is guiding development of drugs against bacterial infection that kills more than 120,000 people each year

A white blood cell ingesting MRSA bacteria shown in a coloured scanning electron micrograph. Wikimedia Commons

The superbug MRSA uses a “double defence strategy” to protect itself against antibiotics, researchers have discovered, in a breakthrough that could pave the way for new treatments.

Antimicrobial resistance, one of the world’s biggest health challenges, occurs when bacteria becomes resistant to antibiotics due to their overuse. Studies show around one million people died each year between 1990 and 2021 as a direct result. MRSA, or methicillin-resistant staphylococcus aureus, currently kills more than 120,000 people each year.

Bacteria grows by splitting in two, requiring enzymes to knit its mesh-like cell walls together. Antibiotic drugs such as penicillin and methicillin target these enzymes to stop bacteria from multiplying. MRSA is known to develop a new layer surrounding its cells that allows it to resist exposure to the drugs designed to kill it. But scientists say that process alone is not enough for it to survive.

Researchers at the University of Sheffield discovered that MRSA has found another way to divide and replicate that allows it to grow in the presence of antibiotics – a process they describe as “hiding in plain sight”.

Prof Simon Foster, from the University of Sheffield’s school of biosciences, told The National this previously unknown process “allows a huge jump in resistance level”. “Using the newly discovered mechanism, the bacteria divide in a different way that does not require a key activity ordinarily needed for them to divide and multiply,” he said.

Prof Foster and his colleagues are now using their knowledge to develop drugs to target this defence mechanism. “It is likely that these new compounds will be used in combination with existing antibiotics. They will be adjuvants and target the resistance mechanism itself,” he said.

Prof Jamie Hobbs, from the university's school of mathematical and physical sciences, said the discovery was the result of bringing physics and biology together to understand antimicrobial resistance. “Our research demonstrates the power of an interdisciplinary approach to address the basic mechanisms supporting the physics of life which are of such importance to healthcare,” he added. The study was published in Science.

Antibacterial resistance does not just pose a danger to the treatment of bacterial infections. Experts have warned that chemotherapy drugs could also be rendered useless against cancer. Around half of all cancer deaths are related to an infection, a figure likely to rise as existing drugs become ineffective.

Scientists are working to develop new types of antibiotics from surprising sources. During a 2020 expedition off Svalbard, an archipelago hundreds of miles north of Norway, researchers found that compounds in types of bacteria called actinobacteria collected from the Arctic Ocean appeared to be able to combat some harmful forms of E. coli.

Actinobacteria from the soil are the source of seven out of 10 current antibiotics. Scientists say compared to actinobacteria in the soil, those found in the sea may even have stronger antibiotic effects.

Bacteria create the substances we use as antibiotics to help them compete against other microorganisms in their natural environment. Any substances released into the oceans are likely to become heavily diluted, so scientists believe ocean-based actinobacteria could produce stronger substances out of necessity, to survive.

“The argument is that in the ocean, compounds need to be more active, more potent, in order to have the same effect on other organisms,” Dr Yannik Schneider, researcher at The Arctic University of Norway in Tromso, previously told The National.